Remotely controlled light sensing apparatus

ABSTRACT

A light control system includes a switching means, a sensing transmitter, and a flash device, connected serially, with the sensing transmitter connected to the flash device by only two wires. The switching means is selectively operable for providing a contact closure to effect the apparent production of a light from the flash device for the illumination of a scene to be photographed. Gating means is responsive to a signal indicative of the firing of the flash device to activate the normally insensitive sensing transmitter to receive light from the scene. A signal to effect the apparent termination of the light provided by the flash device is generated by the sensing transmitter when sufficient light is received from the scene. Dynamic anticipation means provides a time varying compensation for the light intensity-time variation characteristic of flash devices.

United States Patent [191 Ogawa [111 3,714,443 1 1 Jan. 30, 1973 [54]REMOTELY CONTROLLED LIGHT SENSING APPARATUS [52] US. Cl ..250/2l4 P,95/10 R, 307/252 A, 307/311, 315/151, 315/241 P, 328/2 [51] Int. Cl..H01j 39/12 [58] Field of Search...307/252 A, 25 2 B, 252 K, 305,307/311; 328/67, l-5; 315/151, 157, 241 P; 250/205, 214 P; 95/10 R, 10A, 10 B [56] References Cited UNITED STATES PATENTS 3,517,255 6/1970Hoffer et a1. ..315/l5l 3,519,879 7/1970 Ogawa 315/151 Ackermann....

Primary ExaminerStanley D. Miller, Jr. Attorney-Arthur H. Swanson andLockwood D. Burton [57] ABSTRACT A light control system includes aswitching means, a sensing transmitter, and a flash device, connectedserially, with the sensing transmitter connected to the flash device byonly two wires. The switching means is selectively operable forproviding a con-tact closure to effect the apparent production of alight from the flash device for the illumination of a scene to bephotographed. Gating means is responsive to a signal indicative of thefiring of the flash device to activate the normally insensitive sensingtransmitter to receive light from the scene. A signal to effect theapparent termination of the light provided by the flash device isgenerated by the sensing transmitter when sufficient light is receivedfrom the scene. Dynamic anticipation means provides a time varyingcompensation for the light intensity-time variation characteristic offlash devices.

14 Claims, 2 Drawing Figures PATENTED JAN 30 I975 FIG.

SHEET 10F 2 J INVENTOR.

FRANCIS T. OGAWA ATTORNEY.

PATENTEU JAN 3 0 I973 SHEET 2 OF 2 INVENTOR. FRANCIS T. OGAWA BY 2 ZATTORNEY. v

REMOTELY CONTROLLED LIGHT SENSING APPARATUS the art in which the flashof light produced by the flash tube of the system is automaticallyterminated by light responsive sensing transmitter after a predeterminedtotal quantity of light has been received from the scene beingphotographed. While such sensing transmitters have been generallysatisfactory, there has still existed a need for improved sensingtransmitters wherein the actuation of the light terminating means iseffected even more accurately and more reliably under varying conditionsthan has been realized through the use of prior art devices.

Specifically, there has existed a need for an improved sensingtransmitter having greater accuracy, that is, means wherein preciselythe same total quantity of light from a subject is caused to reach alight sensitive film in a camera regardless of the camera to subjectdistance. It has been the tendency of previously known sensingtransmitters to provide excessive amounts of light when the camera tosubject distances are small.

In prior art photographic systems, a light sensing transmitter has beenmounted on or formed as part of a flash device which in turn has beenconnected to a camera means with the standard two conductor connectiontherebetween. When, however, a light sensing transmitter is mounted onor made a part of the camera means, a minimum of three conductors hasbeen required to connect the combination camera-light sensing means withan associated flash device. Additionally, distinct advantages may beobtained by a photographer when the light sensing transmitter of acomputer-flash system is used as an independent member of the system,detached from both the camera means and the flash device as shown incopending application of Roger D. Erickson, Ser. No. 108,877. Thatarrangement is similar to the first mentioned arrangement in that atleast a three wire connection has been .required between the sensingtransmitter and the flash device. Since two wire cables and connectionsare of standard manufacture, there is a need for a light sensingtransmitter requiring only a two wire connection between the lightsensing transmitter and the flash device.

There has also existed a need for an improved light sensing transmitterhaving greater reliability, specifically, a sensing transmitter whichprevents a light terminating means from being actuated by extraneousconditions or events, and is enabled only when it properly should be,that is, when the flash tube of the flash device itself has been fired.The previously known sensing transmitters have often exhibiteddeficiencies in this respect.

It is accordingly an object of the present invention to provide animproved sensing transmitter which obviates the disadvantages of theprior art sensing means.

It is another object of the present invention to provide an improvedsensing transmitter which dynamically compensates for varioussubject-to-camera distances automatically.

It is a further object of the present invention to provide an improvedsensing transmitter compatible with computer flash systems in which thereliability of operation is increased by preventing the untimelyoperation of the flash device, that is, by preventing the lightproducing function from being initiated by noise, the flashing of otherflash devices, and other extraneous causes.

It is'still a further object of the present invention to provide animproved sensing transmitter compatible with computer flash systemswherein the firing of the flash device is the sole condition whichenables the sensing transmitter to become operative.

In accomplishing these and other objects, there has been provided inaccordance with the present invention, an improved sensing transmitterfor use with a switching means and a flash device. The switching meansmay be included as part of a camera means. The above mentioned means areconnected serially with the connection between the sensing means and theflash device comprising only two conductors. The switching means isselectively actuated to activate the flash device for providing a sourcelight which illuminates a scene. When the flash device is activated, thesensing transmitter is enabled and beings to sense the scene light orthe light received from the illuminated scene. When the sensingtransmitter has received a predetermined amount of light from theilluminated scene, a light terminating signal is produced. Dynamicanticipation means is included in the sensing transmitter whereby thepredetermined quantity required to produce the light terminating signalis varied with time, thereby minimizing the unavoidable overexposureerror when the distance between the object being photographed and thecamera means is relatively small. The light terminating signal isreceived by the flash device and is effective to apparently terminatethe light emitted from the flash device.

A better understanding of the present invention may be had from thefollowing detailed description when read in connection with theaccompanying drawings in which:

FIG. 1 is a schematic diagram of a light controlling system employingone embodiment of the sensing transmitter of the present invention.

FIG. 2 is a schematic diagram of a light controlling system employing asecond embodiment of the sensing transmitter of the present invention.

Referring in more detail to FIG. 1, there is shown a control apparatusexemplified by a flash or light producing device, including a capacitor2 connected between two terminals 3 and 7. The two terminals 3 and 7 areconnected to the usual capacitor charging means which are not shown inFIG. 1. Such capacitor charging means are well known in the art and itis sufficient to say that the capacitor 2 is normally maintained in thecharged state by the aforementioned capacitor charging means whereby arelatively high voltage is maintained across the capacitor 2. The highvoltage terminal 3 is connected to a bus 6 and the common terminal 7 isconnected to a bus 8. A flash tube or light producing tube 4 is shownwith its anode connected to the bus 6 and its cathode connected to thebus 8. A light triggering terminal of the flash tube 4 is coupledthrough a transformer T1 to one terminal of a capacitor 10. The otherterminal of the capacitor 10 is connected to the anode terminal of anSCR 98. The common terminal of the transformer T1 is connected to thebus 8. A light terminating tube or quench tube 12 is shown connectedbetween the bus 6 and the bus 8. A triggering terminal 13 of the quenchtube 12, is connected through a transformer T2 to one terminal of acapacitor 14. The other terminal of the capacitor 14 is connected to theanode of a second SCR 90. The common terminal of the transformer T2 isconnected to the common bus 8.

The flash device 1 has two input terminals 74 and 76. Input terminal 76is connected to the common bus 8. The common bus 8 is connected throughtwo resistors 80 and 78 to the common bus 6. The common point betweenthe two resistors 78 and 80 is connected to the signal receiving meansinput terminal 74 and also through a capacitor 84 to a common point 86.The common point 86 is connected through a resistor 88 to the gateterminal of a silicon controlled rectifier (SCR) 90. The gate terminalof the SCR 90 is also connected to the common bus 8 through a resistor92. The cathode terminal of the SCR 90 is directly connected to thecommon bus 8 while the anode terminal is connected to the capacitor 14.The common point 86 is connected through a resistor 102 to a commonpoint between the cathode of the SCR 98 and the anode terminal of adiode 100. The gate terminal of the SCR 98 is connected to the cathodeterminal of the diode 100 which is in turn connected to the common bus8. The common point between the anode of the SCR 98 and the capacitor10, is connected to the bus 6 through a resistor 96. The common pointbetween the anode of the SCR 90 and the capacitor 14, is connected tothe bus 6 through a resistor 94. A light sensing transmitter 15 has afirst pair of terminals 17 and 19. The transmitter 15 may be remotelylocated from the control apparatus 1. The terminals 17 and 19 may beconnected to any switching means, either manual or automaticallycontrolled, to provide a closed contact. In a photographic system theinput terminals 17 and 19 may be connected to a shutter switch of acamera shown in FIG. 1 as 81. Input terminal 17 is connected through aresistor 16 to a common point 18. The parallel combination of a resistor20 and a capacitor 22 connects the common point 18 to a common bus 24 ofthe light sensing means 15. The other input terminal 19 is connected toa bus 26. The bus 26 is connected through two resistors 30 and 32 to thecommon bus 24. The resistor 32 has a sliding arm 34 which connects toajunction 36. Capacitor 38 connects the junction 36 to the common bus24. A sensing means exemplified by light activated silicon controlledrectifier (LASCR) 40 provides a cathode to the anode connection from thejunction 36 to the common point 18. The gate electrode of the LASCR 40is connected through a capacitor 44 and a resistor 46 to the common bus24. A capacitor may be connected between the gate and cathode terminalsof any LASCR shown in the drawings to insure against undesirable noisetriggering the LASCR. The collectoremitter path of an NPN transistor 48connects the gate terminal of the LASCR 40 to the common bus 24. The

base terminal of the transistor 28 is connected through a resistor 54 toa bus 52. A capacitor 56 is connected across the resistor 54. The bus 52is connected to the bus 26 through the collector emitter path of an NPNtransistor 50. A capacitor 39 connects the bus 26 to the common bus 24.The base terminal of the NPN transistor 50 is connected to a commonpoint 60 which is in turn connected through the cathode to anode path ofa zener diode 68 to the common bus 24. The common point 60 is connectedto the collector terminal of the transistor 50 through a resistor 62. Acapacitor 58 is connected between the emitter terminal of the transistor50 and the common point 60. The common point 60 is also connected to theanode of a diode 64, the cathode of which is connected to the bus 52.The bus 52 is connected to the bus 24 through the collectoremitter pathof an NPN transistor 66. The base terminal of the transistor 66 isconnected through a resistor 72 to the common point 18. A capacitor isconnected across the resistor 72. The bus 52 and the bus 24 areconnected to a second pair of terminals 74 and 76', respectively. Thesecond pair of terminals 74' and 76' are connected to thecorrespondingly designated input terminals 74 and 76 of the flash deviceIn FIG. 1, with the SCR 98 nonconducting, the resistor 96 provides acharging path from the high voltage bus 6 to the capacitor 10. Thecapacitor 10 of FIG. 1 will be charged to a steady-state value. When theSCR 98 goes into conduction it provides a low impedance discharge pathfor the capacitor 10. The capacitor 10 is then rapidly discharged. Thataction includes a triggering pulse to appear at the flash tubetriggering terminal 5 and initiates conduction in the flash tube 4.Since the rapid discharge of the capacitor 10 produces a ringing actionin the LC circuit of the capacitor 10 and the transformer T1, the SCR 98will automatically turn off after a triggering pulse has been providedand when the SCR 98 anode voltage is reduced to a level below thethreshold voltage of the SCR 98. Similarly, the resistor 94 provides aconnection between the high voltage bus 6 and the capacitor 14. Thecapacitor 14 of FIG. 1 is charged to a steady state value. When the SCRis made conductive a discharge path is provided for the capacitor 14 anda rapid discharge will occur. That rapid discharge will induce atriggering pulse to appear at the triggering terminal 13 of the quenchtube 12. The quench tube 12 will then begin conduction and the flashtube4 will turn off since the quench tube 12 has a much lower conductingimpedance than the flashtube 4 and the capacitor 2 is effectivelyshort-circuited. The SCR 90 will automatically turn off after atriggering pulse has been provided to the quench tube 12. The automaticturn-off is a consequence of the ringing action through the circuit ofthe capacitor 14 and the transistor T2. A voltage decrease appearing atthe input terminal 74 of the flash device 1 will be coupled through thecapacitor 84 and the resistor 102 to the cathode terminal of the SCR 98.The circuit biasing components associated with the SCR 98 are valued sothat when the negative going signal or voltage decrease appears at theinput terminal 74, the SCR 98 will become conductive and cause theflashtube to begin conduction. Similarly, when a positive going signalor voltage rise appears at the input terminal 74 of the flash device 1,the SCR 90 becomes conductive which causes the operation of the quenchtube and the ultimate termination of the light given off by the flashtube 4. Therefore, when the switch S1 is closed, or first control signalis provided which is operative to effect a first control function, i.e.,the operation of the flashtube and thereby produce an effect, i.e., theproduction of light. A second control signal is subsequently produced bythe sensing transmitter 15 which is operative to effect a second controlfunction, i.e., the operation of the quench tube 12.

The light sensing transmitter 15 operates to transmit the first controlsignal to the remotely located control apparatus and to generate thesecond control signal as is hereinafter explained. The first terminals17 and 19 of the sensing transmitter 15 may be connected to anyswitching means of a light controlling system but for purposes of thepresent example it will be assumed that the terminals 17 and 19 areconnected to the shutter switch of an associated camera as may be usedin a photographic system. Generally in the operation of computer flashdevices used in photographic systems, the shutter switch of a camera isclosed and a light producing means is initiated, thereby providing lightfor a scene to be photographed. A light sensing transmitter measures thelight received from the scene to be photographed and is effective toterminate the apparent light given off by the flash device when apredetermined amount of light has been received by the sensing means.

In FIG. 1, the voltage appearing at the high voltage bus 6 is divided bythe resistors 78 and 88; the resultant is applied to the output terminal74' of the sensing means 15. The biasing circuitry associated with thetransistor 50 effects the conduction of the transistor 50 when thesteady state voltage appears at the output terminal 74'. The currentflowing through the transistor 50 charges the capacitor 39 to a steadystate voltage. That voltage is divided by the two resistors 30 and 32.Normally there is an open contact between the input terminals 17 and 19of the sensing means 15, and therefore, no voltage appears at the commonpoint 18. Since no voltage is at the common terminal 18, the transistor66 is nonconductive and there is no power applied to the sensing meansor LASCR 40. The voltage at the output terminal 74 of the sensing means15 is applied to the base terminal of the transistor 48 through resistor54. The transistor 48 is biased into conduction, thereby providing adischarge path for the capacitor 44. When the LASCR 40 is enabled, acurrent representative of the light received by the LASCR 40 isgenerated through the LASCR gate terminal and accumulates on thecapacitor 44. Since normally the transistor 48 is conductive, no chargeis allowed to be stored on the capacitor 44, thereby eliminating thepossibility that the LASCR 40 will be actuated by ambient light..

When a switching means, such as the shutter switch of the camera,provides a closed contact between the input terminals 17 and 19 of thesensing means 15, the voltage stored by the capacitor 39 causes acurrent to flow from the bus 26 through the terminals 17 and 19 andthrough the resistor 16 to the common point 18 and then through theresistor 20 to the common bus 24. The capacitors 22 and 70 accumulate acharge representative of the voltage appearing at point 18. This voltageis effective to turn on the transistor 66. When the transistor 66 beginsto conduct, the voltage appearing at the output terminal 74 of the lightsensing means exhibits a sudden decrease. This sudden decrease involtage at terminal 74 represents an electrical effect or signal whichcauses the flashtube 4 to fire. The voltage decrease appearing at theterminal 74' is coupled through the diode 64 to the base terminal of thetransistor 50. Therefore when the transistor 66 beings conduction, thetransistor 50 is turned off. The decrease in voltage at the terminal 74is also coupled to the base terminal of the transistor 48 through theresistor 54; the transistor 48 ceases conduction. With an enablingvoltage present at the common point 18 and the transistor 48nonconducting, the sensing means or LASCR 40 is enabled to generate asensor signal or current through its gate terminal representative of theamount of light received from a scene being illuminated by the flashtube4. That current is accumulated on the integrating capacitor 44. Theresistor 46 provides a measure of anticipation as described in U.S. Pat.No. 3,519,879. The charge stored by the capacitor 38, as represented bythe voltage at the point 36, provides a threshold voltage which must beexceeded by the LASCR gate voltage before conduction in the LASCR 40 iseffected. The threshold voltage therefore predetermines the amount oflight which must be received by the LASCR 40 before the LASCR 40 becomesconductive. When the voltage, as represented by the charge stored on thecapacitor 44 biased by the voltage drop across the resistor 46, and thevoltage as represented by the charge stored on the capacitor 38, attaina predetermined relationship, the LASCR 40 becomes conductive. When theLASCR 40 becomes conductive, a relatively low resistance path isprovided for the commonpoint 18 to the common bus 24. The capacitors 22and will now discharge through the LASCR 40, and the voltage at thecommon point 18 will decrease, thereby turning off the transistor 66.When the transistor 66 is turned off, the voltage at the output terminal74' will appear to suddenly increase. That increase in voltage willinitiate the operation of the quench tube and thereby terminate theapparent light from the flash tube 4. After the initiation of conductionin the quench tube 12, the charge stored on the capacitor 2 will rapidlydischarge through the quench tube 12 and when the voltage on the anodeof the quench tube drops to a value insufficient to support ionizationof the tube, the quench tube 12 will again return to its normalnonconductive state. As the quench tube 12 is discharging, the ringingvoltage appearing atthe anode terminal of the SCR will effect selfturn-off of the SCR 90; the SCR 90 will return to its normallynonconductive state. After the quench tube and the flash tube ceaseconduction, the high voltage storing capacitor 2 is again recharged to asteady state value. The transistor 50 will again be biased intoconduction and begin to re-charge the capacitor 38. The restored highvoltage at the output terminal 74' is coupled through the resistor 54 tothe base of the transistor 48 and causes the transistor 48 to againbecome conductive thereby discharging the capacitor 44. After thecharges on the capacitors 22 and 70 have been released through LASCR 40,the voltage at the common point 18 drops to a level whereby the LASCR 40is disabled and the system is ready for another cycle.

In FIG. 2, components similar to those in FIG. 1 are designated with thenumeral shown in FIG. 1 as modified by a prime. FIG. 2 shows a controlapparatus exemplified by a light producing or flash device 1' includinga capacitor 2 connected between two terminals 3 and 7. The two terminals3' and 7' are connected to the usual capacitor charging means which arenot shown in FIG. 2. Such capacitor charging means are well known in theart and it is sufficient to say that the capacitor 2' is normallymaintained in the charged state by the aforementioned capacitor chargingmeans whereby a relatively high voltage is maintained across thecapacitor 2'. The high voltage terminal 3 is connected to a bus 6' andthe terminal 7' is connected to a common bus 8'. A flash or lightproducing tube 4' is shown with its anode connected to the bus 6' andits cathode connected to the bus 8'. A light triggering terminal of theflash tube 4' is coupled through a transformer T1 to one terminal of acapacitor 10'. The other terminal of the capacitor 10' is connected tothe anode terminal of an SCR 156. The common terminal of the transformerT1 is connected to the bus 8'. A light terminating or quench tube 12 isshown connected between the bus 6' and the bus 8. A triggering terminal13' is connected through a transformer T2 to one terminal of a capacitor14'. The other terminal of the capacitor 14' is connected to the anodeterminal of a second SCR 140. The common terminal of the transformer T2is connected to a bus 126.

A capacitor 142 connects the bus 6' with the bus 126. The bus 126 isconnected to the anode of a zener diode 144. The cathode terminal of thezener diode 144 is connected to a common point between the base terminalof an NPN transistor 148 and the cathode terminal of a diode 146. Theanode terminal of the diode 146 is connected to the common bus 8. Thecollector terminal of the transistor 148 is connected through a resistor150 to the anode terminal of the SCR 156. The bus 6 is connected to theanode terminal of the SCR 156 through a resistor 154. The gate terminalof the SCR 156 is connected to the collector terminal of the transistor148, and the cathode terminal of the SCR 156 is connected to the commonbus 8'. The emitter terminal of the transistor 148 is also connected tothe common bus 8'. An input terminal 108 of the flash device 1 isconnected to the bus 126, and the other input terminal 104 of the flashdevice 1 is connected to the common bus 8. The bus 126 is connected tothe emitter terminal of an NPN transistor 130. The base terminal of thetransistor 130 is connected through a capacitor 132 to the common bus8'. The base terminal of the transistor 130 is also connected through aresistor 134 to the high voltage bus 6'. The collector terminal of thetransistor 130 is connected through two resistors 136 and 138 to thehigh voltage bus 6. The common point between the two resistors 136 and138 is connected to the anode terminal of the SCR 140. The gate terminalof the SCR 140 is connected to the collector terminal of the transistor130 and the cathode terminal of the SCR 140 is connected to the bus 126.A sensing transmitter 103, which is remotely located from the controlapparatus 1; has a pair of first terminals 115 and 117. The inputterminal 115 is connected directly to one terminal of a pair of secondterminals 105 and 107. The other input terminal 117 is connected throughthe cathode to anode path of a diode 106 to the other terminal 107 ofthe second terminals. The input terminals and 117 may be connectedexternally to a shutter switch S2 of an associated camera ashereinbefore explained in connection with FIG. 1. The input terminal 115is connected through the anode to cathode path of a diode or gatingmeans 110 to the anode terminal of a sensing means or light activatedsilicon controlled rectifier (LASCR) 111. The anode terminal of theLASCR 111 is also connected through two resistors 112 and 113 to theterminal 107 of the second terminals. The resistor 113 has a slider 114connected to a junction point 116. The point 116 is connected to thecathode terminal of the LASCR 111 and also through a capacitor 118 tothe terminal 107. The gate terminal of the LASCR 111 is connectedthrough the series connection of a capacitor 120 and a resistor 122 tothe terminal 107. The anode terminal of a zener diode 124 is connectedto the terminal 107 and its cathode terminal is connected to the anodeterminal of the LASCR 111. The second terminals 105 and 107 of thesensing means 103 are connected to input terminals 104 and 108 of theflash device 1'.

The circuits shown in FIG. 2 perform the same general functions as thecircuits shown in FIG. 1, however, the sensing transmitter 103 of FIG. 2is a much simpler device than the sensing transmitter 15 shown inFIG. 1. Additionally, the sensing transmitter 103 provides for anenhanced dynamic anticipation as is hereinafter explained. The normallyunpowered feature of the light sensing means 15 of FIG. 1 is retained inthe light sensing means 103 of FIG. 2 as is the need for only a twoconductor connection between the sensing transmitter and the flashdevice. The capacitor 10 of the flash device 1 is charged from the highvoltage bus 6' through the resistor 154. The capacitor 14' of the lightproducing means is similarly charged from the high voltage bus 6'through the resistor 138. The transistor is so biased that it isnormally conducting, in a steady state condition. The transistor 148 issimilarly so biased that it is normally conducting. With the transistor130 conducting, the gate terminal of the SCR is effectively clamped toits cathode terminal and is therefore non-conductive. Similarly with thetransistor 148 conducting the gate terminal of the SCR 156 iseffectively clamped to its cathode terminal thereby precludingconduction. When a switching means, for example the shutter switch S2 ofan associated camera, provides a contact closure between the inputterminals 115 and 117 of the sensing transmitter 103, a current flowsfrom the bus 126, through the diode 106, to the bus 8. At that time, theLASCR will be still disabled since the diode 110 is reverse biased. Thevoltage on the bus 126 decreases since a lower resistance path (diode106) is now present between the buses 126 and 8' than was present beforethe switch S2 closure(zener 144 and base emitter path of transistor148). The lower voltage on the bus 126 with respect to the bus 8' willcause the transistor 148 to turn off. With the transistor 148 open, acurrent will flow through the resistor 150 and into the gate terminal ofthe SCR 156, thereby rendering it conductive. With the SCR 156conducting, a relatively low resistance path rapidly discharges thecapacitor thereby initiating the light producing function of the flashtube 4' as hereinbefore explained. As the flash tube 4' begins toconduct, the voltage on the bus 6' is suddenly reduced as the charge onthe capacitor 2' is dumped through the flash tube 4'. That suddenvoltage decrease of the high voltage bus 6' is coupled through thecapacitor 142 to the bus 126. The coupling action of the capacitor 142causes the voltage on the bus 126 to suddenly decrease to a negativevalue with respect to the bus 8. The negative voltage on the bus 126with respect to the bus 8' is coupled to the sensing transmitter 103through the terminals 104 and 108. Normally, then, the voltage at theoutput terminal 107 of the sensing transmitter 103 is positive withrespect to the voltage appearing at the output terminal 105 and thegating means or diode 110 will prevent conduction in the light sensingcircuit since it is normally reverse biased. However, as is nowapparent, when the flash tube 4 begins to conduct, the voltage at theoutput terminal 105 of the light sensing means 103 becomes positive withrespect to the voltage appearing at the output terminal 107. The gatingmeans or diode 110 will then be forward biased and allow a current toflow therethrough. The diode 106 will then be reverse biased therebyeffectively disconnecting the switching means from the circuits. Thecurrent flowing through the diode 110 flows through the resistor 112 andresistor 113. That current establishes a voltage at the anode of theLASCR 111 which effectively powers or enables the sensing means or LASCR111. The time interval between the activation of the switching means S2connecting the input terminals 115 and 117 of the light sensing means103 and the powering of the LASCR 111, is relatively short and thereforeonly a momentary contact is required from the switching means S2 for theproper operation of the system. A portion of the current flowing throughthe resistor 112 flows through the slider 114 and begins to charge thecapacitor 118. When the sensing means or LASCR 111 is enabled, a sensorsignal or current representative of the amount of light received therebyflows through its gate terminal to the integraging capacitor 120 andthrough the anticipation resistor 122. The function of the anticipationresistor 122 is fully explained in US. Pat. No. 3,519,879. The capacitor118 provides a unique type of dynamic anticipation in addition to theanticipation resistor 122. The cooperative operation is this particularportion of the circuit will be hereinafter explained. For now however,it is sufficient to say that when the voltage stored by the integratingcapacitor 120 as biased by the anticipation resistor 122, exceeds thevoltage representative of the charge stored on the dynamic anticipationcapacitor 118, the LASCR 111 becomes conductive thereby providing a lowresistance path and an associated voltage decrease between the outputterminals 105 and 107, and consequently between the bus 126 and the bus8. That voltage decrease is coupled through the capacitor 132 to thebase terminal of the transistor 130 thereby causing the transistor 130to turn off. With the transistor 130 non-conducting, a current will flowinto the gate terminal of the SCR 140 thereby rendering it conductive.When the LASCR 140 becomes conductive a lower resistance path ispresented to the capacitor 14 of the flash device 1' which causes thecapacitor 14 to dump its charge. That action induces a triggering signalto appear at the quench tube triggering terminal 13' thereby initiatingconduction in the quench tube 12'. The rapid discharge of the capacitor14' produces a ringing action through the circuit comprising thecapacitor 14', the SCR 140, and the transformer T2. This ringing actionis effective to turn off the SCR 140 after the quench tube triggeringsignal has been provided. After the quench tube 12' fires, the chargestored on the capacitor 2' of the light producing means 1 will disipateto a point where the voltage on the bus 6' is insufficient to supportionization in the quench tube 12' and the quench tube 12' will thereforeturn off. The charging circuit connected to the terminals 3 and 7' ofthe light producing means 1' will begin to re-charge the capacitor 2.The voltage appearing at the bus 6' will build up to a value sufficientto restore biasing voltage required to turn the transistors 130 and 148on and the system shown in FIG. 2 will be returned to its normalcondition to await the initiation of another cycle.

Dynamic anticipation acts to insure proper exposure of the lightsensitive film in a camera even though the camera to subject distance isrelatively small. The operation of anticipation circuitry including theintegrating capacitor 120 the anticipation resistor 122 of FIG. 2 isexplained in detail in US. Pat. No. 3,519,879. That inventionessentially provided means whereby a turn-on voltage representative ofan amount of light received by a light sensing means would automaticallyreflect the steep initial rise in light intensity when a flash tube isinitiated. The use of the capacitor 118, the resistor 112 and theportion of the resistor 113 above the slide wire 114, provides animprovement over the circuitry shown in the above referenced patent. Inthat ceeded the threshold voltage present at the cathode terminal of theLASCR. The threshold voltage which had to be exceeded had been set at afixed value heretofore. For example a curve may be plotted with v thevoltage representative of the light received as the ordinate and time asthe abcissa. At a time T the voltage representative of the lightreceived will exceed the fixed threshold voltage on the cathode of anLASCR the LASCR will become conductive. With the dynamic anticipationmeans in the present invention, the threshold voltage is not fixed butis initially zero volts and is increased with time as determined by theRC time constant of the resistor 112, the portion of the resistor 113above the slide wire 114, and the dynamic anticipation capacitor 18.Using the dynamic anticipation means threshold voltage appearing atpoint 116 will be exceeded by the turnon voltage representative of thelight exceeded by the turn-on voltage representative of the lightreceived by the LASCR 111 at a time T1 which occurs prior to theaforementioned time T. Therefore the LASCR 111 will be turned on soonerwith the dynamic anticipation means and the over-exposure error due toadditional light received after sufficient film exposure light hasalready been received, is reduced to a minimum. The over-exposure erroravoided through the use of the dynamic anticipation means hereindisclosed, is proportional to the light received by the camera betweenthe two times T and T1.

Thus there has been provided an improved sensing transmitter for usewith a switching means, and a flash device connected serially whereby anactuation of the switching means initiates the production of a sourcelight from the flash device for the illumination of a scene, and thelight sensing means is responsive to the scene light or the lightreceived from the illuminated scene to generate a light terminating orquench signal effective to arrest the apparent production of light. Theswitching means may be part of an associated camera means. The improvedsensing means is characterized by the use of a unique dynamicanticipation means which minimizes the over-exposure error heretoforeunavoidable, especially in situations where the object to cameradistance is relatively small. The improved sensing means is furthercharacterized in that only two conductors are required to connect thesensing means with the flash device.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A sensing transmitter for use with a remotely located controlapparatus, said sensing transmitter comprising:

a first pair of terminals and a second pair of terminals,

said first pair of terminals providing a connection to means forproviding a first control signal,

said second pair of terminals providing a connection to said remotelylocated control apparatus,

all energizing power for said sensing transmitter being applied to saidsecond pair of terminals from said remotely located control apparatus,

said sensing transmitter further including means for transmitting saidfirst control signal, through said second pair of terminals, to saidremotely located control apparatus to effect a first control functionthereat,

sensing means for monitoring an effect produced as a result of saidcontrol function and providing a sensor signal in variable accordancetherewith,

and means responsive to said sensor signal for providing a secondcontrol signal whenever said sensor signal reaches a predeterminedvalue, said second control signal also being applied to said second pairof terminals for transmission to said remotely located control apparatusto effect a second control function thereat.

2. A sensing transmitter as set forth in claim 1 and furthercharacterized by the inclusion of gating means therein which normallymaintains said sensing means in an inoperative condition, said gatingmeans being responsive to a signal applied to said second pair ofterminals indicative of the occurrence of said first control functionfor rendering said sensing means operative.

4. The invention as set forth in claim 3 wherein said i gating means isa diode having an anode terminal and a cathode terminal, said diodeanode terminal being connected to a first terminal of said first pair;and wherein said sensing means and said means responsive to said sensorsignal comprise a Light Activated Silicon Controlled Rectifier (LASCR)having anode, cathode and gate terminals, said sensing means being alight responsive junction of said LASCR, said anode terminal of saidLASCR being connected to said diode cathode terminal; said signaltransmitter further including an integrating capacitor and ananticipation resistor connected in series between said LASCR gateterminal and a second terminal of said second pair; and said means forproviding a time-varying threshold signal including: a capacitorconnected between said LASCR cathode terminal and said second terminalof said first pair; and a voltage divider connecting said diode cathodeterminal with said second terminal of said first pair, said voltagedivider having a pick-off terminal thereon connected to said LASCRcathode terminal.

5. A sensing transmitter as set forth in claim 2 and furthercharacterized by the inclusion of isolating means responsive to saidlast mentioned signal for effectively isolating said sensing transmitterfrom said means for producing said first control signal during thecontinuance of said signal applied to said second pair of terminalsindicative of the occurrence of said first control function.

6. The invention as set forth in claim 5 wherein said isolating means isa diode having an anode terminal coupled to a second terminal of saidfirst pair, and a cathode terminal coupled to said second terminal ofsaid first pair.

7. The invention as set forth in claim 1 wherein said means fortransmitting said first control signal includes:

a first transistor having base, collector, and emitter terminals saidcollector and emitter terminals being connected respectively to a firstterminal of said second pair and a first terminal of said first pair; aresistor connecting said base terminal with said collector terminal; afirst and second terminals diode having anode and cathode terminals,

said cathode terminal being connected to said base terminal and saidanode terminal being connected to a second terminal of said second pair;a first voltage divider means connecting a second'terminal of said firstpair with said second terminal of said second pair, said first voltagedivider means having a pick-off terminal thereon; a second transistorhaving base collector and emitter terminals, said collector and emitterterminals of said second transistor being connected respectively betweensaid first and second terminals of said second pair; a second diodehaving an anode terminal connected to said base terminal of said firsttransistor and a cathode terminal connected to said collector terminalof said first transistor; a first capacitor means connecting saidemitter and base terminals of said first transistor; a second capacitormeans connected between said pick-off terminal and said base terminal ofsaid second transistor; and a third capacitor means connected betweensaid pick-off terminal and said second terminal of said second pair.

8. The invention as set forth in claim 7 wherein said sensing means andsaid means responsive to said sensor signal comprise:

a light activated silicon controlled rectifier (LASCR) having anodecathode and gate terminals, said sensing means being a light responsivejunction of said LASCR, said anode terminal of said LASCR beingconnected to said pick-off terminal; a first charge storage meansconnected between said first terminal of said first pair and said secondterminal of said second pair; a second voltage divider means connectedacross said first charge storage means, said second voltage dividerhaving a pick-off terminal connected to said cathode terminal of saidLASCR; a second charge storage means connected between said cathodeterminal of said LASCR and said second terminal of said second pair; anintegration means connected between said gate terminal of said LASCR andsaid second terminal of said second pair, said integration means forintegrating said sensor signal; and a third transistor having base,collector and emitter terminals, said collector and emitter terminals ofsaid third transistor being connected across said integration means, andsaid base terminal of said third transistor being connected to saidfirst terminal of said second pair.

9. The invention as set forth in claim 8 wherein said first and secondcharge storage means are capacitors, and said integration meansincludes:

a capacitor and a resistor serially connected between said gate terminalof said LASCR and said second terminal of said second pair.

10. The invention as set forth in claim 1 wherein said means forproviding a first control signal includes a shutter switch of aphotographic camera.

11. The combination comprising:

means for providing a first control signal;

first pair of terminals and second pair of terminals, said first pair ofterminals providing a connection means to said means for providing saidfirst control signal, said second pair of terminals providing aconnection means to a remotely located control apparatus,

all energizing power for said sensing transmitter being applied to saidsecond pair of terminals from said remotely located control apparatus,

means for transmitting said first control signal through said secondpair of terminals to said remotely located control apparatus to effect afirst control function thereat;

sensing means for monitoring an effect produced as a result of saidcontrol function and providing a sensor signal in variable accordancetherewith; and

means responsive to said sensor signal for providing a second controlsignal whenever said sensor signal reaches a predetermined value, saidsecond control signal also being applied to said second pair ofterminals for transmission to said remote] located control apparatus toeffect a second con rol function thereat.

12. The invention as set forth in claim 11 wherein said means forproviding said first control signal includes a shutter switch of aphotographic camera.

13. The sensing transmitter as set forth in claim 1 wherein said meansfor transmitting said first control signal includes first and secondconnection means connecting respective terminals of said first andsecond pair of terminals.

14. The sensing transmitter as set forth in claim 13 wherein saidsensing means and said means responsive to said sensor signal comprise:

a first diode means having anode and cathode terminals, said anodeterminal being connected to said first connection means,

a light activated silicon controlled rectifier (LASCR) having anode,cathode, and gate terminals, said LASCR anode terminal being connectedto said first diode cathode terminal,

an integrating means connecting said LASCR gate terminal with saidsecond connection means,

a voltage divider means connected between said first diode cathodeterminal and said second connection means, said voltage divider meanshaving a pick off terminal thereon connected to said LASCR cathodeterminal,

a capacitor means connecting said LASCR cathode terminal with saidsecond connection means, and

a second diode means having an anode terminal connected to said secondconnection means, and a cathode terminal connected to said first diodecathode terminal.

1. A sensing transmitter for use with a remotely located controlapparatus, said sensing transmitter comprising: a first pair ofterminals and a second pair of terminals, said first pair of terminalsproviding a connection to means for providing a first control signal,said second pair of terminals providing a connection to said remotelylocated control apparatus, all energizing power for said sensingtransmitter being applied to said second pair of terminals from saidremotely located control apparatus, said sensing transmitter furtherincluding means for transmitting said first control signal, through saidsecond pair of terminals, to said remotely located control apparatus toeffect a first control function thereat, sensing means for monitoring aneffect produced as a result of said control function and providing asensor signal in variable accordance therewith, and means responsive tosaid sensor signal for providing a second control signal whenever saidsensor signal reaches a predetermined value, said second control signalalso being applied to said second pair of terminals for transmission tosaid remotely located control apparatus to effect a second controlfunction thereat.
 1. A sensing transmitter for use with a remotelylocated control apparatus, said sensing transmitter comprising: a firstpair of terminals and a second pair of terminals, said first pair ofterminals providing a connection to means for providing a first controlsignal, said second pair of terminals providing a connection to saidremotely located control apparatus, all energizing power for saidsensing transmitter being applied to said second pair of terminals fromsaid remotely located control apparatus, said sensing transmitterfurther including means for transmitting said first control signal,through said second pair of terminals, to said remotely located controlapparatus to effect a first control function thereat, sensing means formonitoring an effect produced as a result of said control function andproviding a sensor signal in variable accordance therewith, and meansresponsive to said sensor signal for providing a second control signalwhenever said sensor signal reaches a predetermined value, said secondcontrol signal also being applied to said second pair of terminals fortransmission to said remotely located control apparatus to effect asecond control function thereat.
 2. A sensing transmitter as set forthin claim 1 and further characterized by the inclusion of gating meanstherein which normally maintains said sensing means in an inoperativecondition, said gating means being responsive to a signal applied tosaid second pair of terminals indicative of the occurrence of said firstcontrol function for rendering said sensing means operative.
 3. Theinvention as set forth in claim 2, wherein said means responsive to saidsensor signal further includes means for providing a time-varyingthreshold signal whereby said second control signal is provided wheneversaid sensor signal and said threshold signal attain a predeterminedrelationship.
 4. The invention as set forth in claim 3 wherein saidgating means is a diode having an anode terminal and a cathode terminal,said diode anode terminal being connected to a first terminal of saidfirst pair; and Wherein said sensing means and said means responsive tosaid sensor signal comprise a Light Activated Silicon ControlledRectifier (LASCR) having anode, cathode and gate terminals, said sensingmeans being a light responsive junction of said LASCR, said anodeterminal of said LASCR being connected to said diode cathode terminal;said signal transmitter further including an integrating capacitor andan anticipation resistor connected in series between said LASCR gateterminal and a second terminal of said second pair; and said means forproviding a time-varying threshold signal including: a capacitorconnected between said LASCR cathode terminal and said second terminalof said first pair; and a voltage divider connecting said diode cathodeterminal with said second terminal of said first pair, said voltagedivider having a pick-off terminal thereon connected to said LASCRcathode terminal.
 5. A sensing transmitter as set forth in claim 2 andfurther characterized by the inclusion of isolating means responsive tosaid last mentioned signal for effectively isolating said sensingtransmitter from said means for producing said first control signalduring the continuance of said signal applied to said second pair ofterminals indicative of the occurrence of said first control function.6. The invention as set forth in claim 5 wherein said isolating means isa diode having an anode terminal coupled to a second terminal of saidfirst pair, and a cathode terminal coupled to said second terminal ofsaid first pair.
 7. The invention as set forth in claim 1 wherein saidmeans for transmitting said first control signal includes: a firsttransistor having base, collector, and emitter terminals said collectorand emitter terminals being connected respectively to a first terminalof said second pair and a first terminal of said first pair; a resistorconnecting said base terminal with said collector terminal; a first andsecond terminals diode having anode and cathode terminals, said cathodeterminal being connected to said base terminal and said anode terminalbeing connected to a second terminal of said second pair; a firstvoltage divider means connecting a second terminal of said first pairwith said second terminal of said second pair, said first voltagedivider means having a pick-off terminal thereon; a second transistorhaving base collector and emitter terminals, said collector and emitterterminals of said second transistor being connected respectively betweensaid first and second terminals of said second pair; a second diodehaving an anode terminal connected to said base terminal of said firsttransistor and a cathode terminal connected to said collector terminalof said first transistor; a first capacitor means connecting saidemitter and base terminals of said first transistor; a second capacitormeans connected between said pick-off terminal and said base terminal ofsaid second transistor; and a third capacitor means connected betweensaid pick-off terminal and said second terminal of said second pair. 8.The invention as set forth in claim 7 wherein said sensing means andsaid means responsive to said sensor signal comprise: a light activatedsilicon controlled rectifier (LASCR) having anode cathode and gateterminals, said sensing means being a light responsive junction of saidLASCR, said anode terminal of said LASCR being connected to saidpick-off terminal; a first charge storage means connected between saidfirst terminal of said first pair and said second terminal of saidsecond pair; a second voltage divider means connected across said firstcharge storage means, said second voltage divider having a pick-offterminal connected to said cathode terminal of said LASCR; a secondcharge storage means connected between said cathode terminal of saidLASCR and said second terminal of said second pair; an integration meansconnected between said gate terminal of said LASCR and said secondterminal of said second pair, said inTegration means for integratingsaid sensor signal; and a third transistor having base, collector andemitter terminals, said collector and emitter terminals of said thirdtransistor being connected across said integration means, and said baseterminal of said third transistor being connected to said first terminalof said second pair.
 9. The invention as set forth in claim 8 whereinsaid first and second charge storage means are capacitors, and saidintegration means includes: a capacitor and a resistor seriallyconnected between said gate terminal of said LASCR and said secondterminal of said second pair.
 10. The invention as set forth in claim 1wherein said means for providing a first control signal includes ashutter switch of a photographic camera.
 11. The combination comprising:means for providing a first control signal; first pair of terminals andsecond pair of terminals, said first pair of terminals providing aconnection means to said means for providing said first control signal,said second pair of terminals providing a connection means to a remotelylocated control apparatus, all energizing power for said sensingtransmitter being applied to said second pair of terminals from saidremotely located control apparatus, means for transmitting said firstcontrol signal through said second pair of terminals to said remotelylocated control apparatus to effect a first control function thereat;sensing means for monitoring an effect produced as a result of saidcontrol function and providing a sensor signal in variable accordancetherewith; and means responsive to said sensor signal for providing asecond control signal whenever said sensor signal reaches apredetermined value, said second control signal also being applied tosaid second pair of terminals for transmission to said remotely locatedcontrol apparatus to effect a second control function thereat.
 12. Theinvention as set forth in claim 11 wherein said means for providing saidfirst control signal includes a shutter switch of a photographic camera.13. The sensing transmitter as set forth in claim 1 wherein said meansfor transmitting said first control signal includes first and secondconnection means connecting respective terminals of said first andsecond pair of terminals.